Ferroresonant transformer with saturating control winding



P 8, 1964 o. M. BAYCURA ETAL' 3,148,326

FERRQRESONANT TRANSFORMER WITH SATURATING CONTROL WINDING Filed Dec. 24, 1959 2 Sheets-Sheet 1 24 (M8 1 22 O-ao FIG.6

INVENTOES ORESTES M. BAYCURA, ET AL BYQ MQL. U-

A 77'0RNE Y Sept. 8, 1964 o. M. BAYCURA ETAL 3,143,326 FERRORESONANT TRANSFORMER WITH 'SATURAT'ING comm. WINDING Filed Dec. 24, 1959 2 Sheets-Shet 2 FIG.9

United States Patent 3,148,326 FERRORESONANT TRANSFORMER WITH SATURATING CONTROL WINDING Orestes M. Baycura, Endicott, Donald F. Busch, Vestal, Pierre Essinger, Endicott, and John F. ODonnell, Apalachin, N.Y., assignors to International Business Machines Corporation, New York, N.Y., a corporation of New York Filed Dec. 24, 1959, Ser. No. 861,840 11 Claims. (01.323-56) This invention relates generally to transducers and has reference in particular to regulating means for transformers and the like having means for producing a local control flux for varying the inductive coupling between input and output windings thereof.

More specifically, it is. an object of this invention to provide in a transformer for regulating the output voltage by varying a local magnetic flux in a portion of a magnetic path in the transformer.

Another object of this invention is to provide a simple and effective control for magnetic core transducers by utilizing a control flux that alters the swing of the B-H curve in the flux direction without altering it in the other direction.

Yet another object of the invention is to provide in a transformer for utilizing a winding with either a DC. or AC. control source for introducing a control flux in a portion of a magnetic circuit for regulating the output of the transformer without distorting the wave form thereof.

It is another object of this invention to provide for regulating the output voltage of a transformer by introducing a control flux in a portion of the magnetic circuit that is orthogonal at least in part to the main flux in said portion.

A further object of the invention is to provide in a ferroresonant transformer for introducing a control flux into a portion of a magnetic circuit so as to reduce the effective cross-section of that portion.

Another important object of the invention is to utilize a conductor in a hole through a portion of a magnetic core of a transformer for introducing a peripheral saturating control flux in the vicinity of the hole and thereby changing the eifective coupling between primary and secondary windings Without distorting the wave form of the output voltage.

A further important object of the invention is to provide for utilizing a control winding in a transformer having a figure 8 configuration for introducing a control flux and varying the effective cross-section of a core section in the transformer to control the output voltage thereof.

Yet another important object of this invention is to provide for using a cross-field flux in a transformer for regulating the output voltage thereof.

Still another important object of this invention is to provide in a transformer for utilizing a winding within a portion of the core for producing a control flux orthogonal to the regular flux path for controlling the output voltage.

The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings.

In the drawings:

FIG. 1 is a schematic diagram of a ferroresonant transformer utilizing the invention in one of its forms.

FIG. 2 is a schematic diagram of a ferroresonant transformer utilizing the invention in another of its forms.

FIG. 3 is a schematic showing of a magnetic shunt, such as utilized in the transformers of FIGS. 1 and 2 illustrating yet another embodiment of the invention.

FIG. 4 shows a series of B-H curves illustrating characteristic magnetization curves for transformers embodying the invention.

FIG. 5 is a schematic diagram of a regular type of alternating current transformer utilizing the invention in one of its forms.

FIG. 6 is a schematic showing of a regular type transformer utilizing the invention in accordance with another of its forms.

FIG. 7 is a schematic showing of yet another arrangement of a transformer utilizing a cross-field control fluX.

FIG. 8 is a schematic diagram showing a regulated ferroresonant transformer control system embodying the invention.

FIG. 9 is a schematic diagram showing another application of the invention to a ferroresonant transformer incorporating a temperature compensating feature.

Referring particularly to FIG. 1 of the drawings, the reference numeral 10 denotes generally a ferroresonant regulating transformer of the type disclosed in Patent No. 2,143,745, which issued on January 10, 1939, to Joseph G. Sola, entitled Constant Potential Transformer. Briefly, the transformer 10 comprises a 3-legged magnetic core having outer legs 10a and 1% with a central leg having primary and secondary portions 10A and 10B, respectively, the legs being connected by end portions 11 and 12. A primary winding 13 is positioned on the primary section 10A and a secondary winding 14 is positioned on the secondary portion 10B. The primary winding 12 may be connected to a suitable source of alternating current while the secondary winding 14 may be connected to any suitable load circuit, not shown. A capacitor 15 is connected across a portion of the secondary winding 14 to provide a resonant circuit condition therewith for effecting saturation of the secondary portion of the core 10B in the manner described in detail in the Sola Patent 2,143,745 hereinbefore referred to. The legs 10a and 10b are provided with magnetic shunt portions 17 and 18 which extend between the central leg and the outer legs and provide a shunt magnetic circuit intermediate the primary and secondary windings. These shunt portions may equally well comprise portions of the central leg.

In order to provide for further regulating the output voltage of the secondary winding 14 over and above the inherent regulation of such a transformer, a hole or opening, such as the slot 20, is provided in the secondary portion 163 of the central leg for accommodating a control winding 22 which is either threaded through the hole in a figure 8 configuration 0r comprises separate winding 22a, 221) about the two portions of the center leg portion 10B on either side of the slot 20, connected in opposite senses to provide an effective figure 8 winding as shown. By connecting terminals 24 and 25 of the control winding 22 to a suitable source and varying the current through the control winding, the saturation of the core portion 10B immediately adjacent the hole 20 may be effected, and the output voltage of the winding 14 may be readily regulated. While the control winding 22 is shown as connected to a direct current source, as a battery 26, this is only illustrative, and it will be realized that other types of sources may be used including an alternating current source if the phase of the voltage applied to the control winding is in phase with a current in the secondary winding 14. For ordinary transformers, it should be in phase with the primary current. Likewise, holes 28 and 30 may be provided in other portions of the secondary circuit for accommodating control windings similar to the winding 22 for similarly controlling the output voltage of the secondary winding 14.

Referring to FIG. 2, it will be seen that a similar ferroresonant transformer 10 having a 3-legged core with outer legs 10a and 10b and a central leg having primary and secondary portions 10A and 10B, respectively, provided with primary and secondary windings 13 and 14 similar to that described in connection with the transformer of FIG. 1, may be provided with a control winding 30 having input terminals 31 and 32, respectively. The control winding 30, instead of being formed in a figure 8 configuration as is the control winding of FIG. 1, is embedded in the core of the transformer 10 being, for example, located either between larninations or in a central opening drilled or otherwise provided throughout the length of the outer legs 10a and 10b and through the end connecting portion 11 of the core. The winding 30 may, for example, as shown in the embodiment in connection with FIG. 3, be positioned in an opening 29 drilled longitudinally of the core so as to provide a cross-field flux throughout the length of the conductor which is orthogonal to the principal flux of the transformer to the core portions in which it lies.

By connecting the control winding terminals 31 and 32 to a suitable source of control voltage, as described in connection with the winding 22 of FIG. 1, the magnetization curve of the core'may be affected as shown by the family of B-H magnetization curves in FIG. 4 wherein the curve a represents the magnetization or magnetic flux vs. ampere drive characteristic of the core without any current in the control winding, the curve b represents the modified magnetization characteristic with a nominal value of current in the control winding and the magnetization curve c represents the configuration of the magnetization characteristic curve with a still greater value of current in the control winding. It will be noted that in all instances the symmetry of the curves is retained, and the effect of the current in the control winding is merely to shift the curve in the vertical 'or flux direction without altering its symmetry or changing the swing of the curve in the drive or current direction. By thus varying the characteristics of the principal flux in the core of the transformer, it is possible to vary the output voltage of winding 14, since the net change in principal flux is varied, without introducing the distortion in wave form which usually accompanies the use of a direct current control winding which merely biases the magnetization curve so that further operation is merely on a restricted or minor portion of the curve, instead of over the principal portion thereof as shown by the family of curves in FIG. 4.

Instead of utilizing a control of winding 30 embedded directly in the outer legs of the transformer as shown in FIG. 2, a similar cross-field control winding 34 having terminals 35 and 36 may be utilized, for example, in connection with the magnetic shunts 17 and 18 which are shown in FIG. 2 as connected to the outer legs 10a and 10b although they may equally well be connected to the centerrleg. It will be realized that these two arrangements are the full equivalents of each other. As shown in FIG. 3, the magnetic shunt 17 is made wider than normal, and an opening 38 is provided through the additional portion of the shunt for accommodating the control winding 34, instead of placing the control winding in the principal portion of the shunt. When connected to a suitable source of control voltage, the control winding 34 operates in substantially the same manner as the control winding 30 of FIG. 2 to produce a cross-field or orthogonal flux around the winding 34 which is perpendicular to the principal flux linking the primary and secondary windings 13 and 14 and effects the saturation of shunt as to alter the characteristic magnetization curve in a manner as shown in FIG. 4.

Referring to FIG. 5, the reference numeral 40 denotes an alternating current transformer having a primary winding 41 and a secondary winding 42 positioned on legs 43 and 44 of a magnetic core 45 having a third .or central leg 46. A control winding 48 having terminals 49 and 50 is disposed to be wound in a figure 8 configuration through a hole 52 in the shunt leg portion 46 of the core 45. By applying a suitable control potential to the control winding 48, as from a potentiometer P connected to the same source as the primary winding 41, a saturating flux is produced about the periphery of the opening 52 which operates to modify the magnetization curve of the core 45 in a manner similar to that of the control windings 22 and 30 of FIGS. 1 and 2, so as to vary the fiux linkages between the primary winding 41 and the secondary winding 42 and thereby vary the output voltage of the secondary winding 42.

Referring to FIG. 6, it will be seen that a transformer 52 comprises a core 55 having primary and secondary windings 57 and 59 thereon in the usual manner. A control winding 62 is further threaded through openings in the core legsin a manner similar to that of FIGS. 2 and 3 so as to provide a cross-field or orthogonal flux therein for modifying the magnetization characteristics in the manner illustrated by the curves of FIG. 4 and controlling the output voltage of the secondary winding 59.

Referring to FIG. 7, it will be seen that a transformer 65 comprises a ring-type core 66 having inductively related primary and secondary windings 68 and 69 thereon in the well-known manner. In order to utilize the crossfield principle of controlling the flux in the core 66 for varying the output voltage of the secondary winding 69, means such as the C-shaped core 70 may be provided having pole pieces 71 and 72 disposed on opposite sides of a portion of the core 66. The core 70 is provided with a control winding 75 having terminals 76 and 77 for connection to a source of control voltage for producing a cross-field flux between the pole pieces 71 and 72. This flux traverses the core 66 in a direction which is orthogonal to the principal flux of the transformer 65 for varying the magnetization characteristics thereof in the manner illustrated in the curves of FIG. 4, thereby varying the effective change in flux, the inductive coupling of the windings, and hence the secondary voltage.

Referring to FIG. 8, the reference numeral 10 denotes schematically the transformer of the type such as shown in FIGS. 1 and 2 comprising a core having primary and secondary portions 10A and 10B separated by magnetic shunt members 17 and 18 and having a primary winding 12 on the primary portion which is connected to a source of alternating current, such as the generator 16, and a secondary winding 14 which in this instance is shown connected through rectifiers 21 to a load circuit 23. The capacitor 15 is connected across a portion of the secondary winding 14 for producing a resonant circuit condition therein as explained in connection with the transformers of FIGS. 1 and 2. The secondary portion 10B of the core is provided with a control winding 72 corresponding to the winding 22 of FIG. 1 and having a figure 8 configuration as shown in connection with the transformer of FIG. 1 for effecting control of the output voltage of the winding 14.

In order to provide for closely regulating the voltage applied to the load circuit 23, a feed-back amplifier is utilized having means such as an adjustable potentiometer P for applying a portion of the load circuit voltage to the base of a transistor X5, which together with an associated transistor X4 comprises a differential amplifier. Transistor X5 controls transistor X4 through resistor R3. The base of the transistor X4 is connected to obtain a fixed bias from a Zener diode Z. The transistor X4 is utilized to vary the current through a resistor R1 for controlling the conductivity of an amplifier transistor X3.

This transistor X3 is connected through a resistor R2 to control the bias on companion amplifier transistor X2 which in turn controls through R4 the bias of a power amplifier transistor X1 connected in circuit with the control winding 22 and the terminals of, for example, a 6- volt direct current source for controlling the current through the control winding.

As hereinbefore set forth, the transistors X4'and X5 together comprise a differential amplifier. 'All transistors shown are of the PNP type, though it will be realized that NPN types could be used with other circuit arrangements. The bias of the transistor X4 is fixed by the voltage across the Zener diode Z. Accordingly, if the voltage of the load circuit and hence the voltage from the potentiometer P decreases, the base of the transistor X5 is made more positive with respect to its emitter, and it is driven towards cut-off. When the transistor X5 cuts off, the transistor X4 is driven further towards conduction as there is less drop through the common emitter resistor R3. As more current is drawn by the transistor X4, this biases off the transistor X3. This in turn tends to turn transistor X2 off, reducing the current drawn through the resistor R4 and thus reducing the conductivity of the power amplifier transistor X1. Less current is supplied to the control winding 22, so a greater change in flux is experienced in the core of the transformer 10, and the output voltage goes up to restore the original condition.

Referring to FIG. 9, it will be seen that a similar transformer is likewise provided with a figure 8 control winding 72 controlled by a series transistor X1 is conjunction with transistors X2 through X5 as described in connection with the circuit of FIG. 8. By inserting a thermistor T in series with the potentiometer P having a control resistor CR connected in shunt therewith, control over the current in the winding 22 may be effected in accordance with the temperature variations of the thermistor T which may have a negative or a positive temperature resistance characteristic corresponding, for example, to a particular load characteristic for compensating for the voltage applied to the load circuit 23 in accordance with a temperature characteristic thereof, such as, where the load is for example the drivers of a magnetic core memory device or the like. As the temperature of the load device changes the thermistor T effects a compensating change by varying the voltage from the potentiometer P accordingly. In other respects the circuit operates similar to that described in connection with the circuit of FIG. 8.

From the above description, it will be seen that by utilizing a control winding in accordance with the feature of this invention symmetrical operation of transformers may be effected so that the output wave form is not dis torted as when direct current saturating windings are used. Accordingly, such transformers may be used directly for power applications and the need for expensive filtering is reduced. While control circuits have been shown connected to the figure 8 control winding of a ferroresonant core, it will be realized that any of the control windings for any of the transformers may be controlled by either of these circuits or other such control circuits for controlling or regulating the output voltage.

While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that the foregoing and other changes in form and details may be made therein without departing from the spirit and scope of the invention.

What is claimed is:

1. In a ferroresonant transducer, a magnetic core, means including an alternating current winding on said core coupled by a principal flux for supplying alternating current energy to a load circuit, a capacitor coupled to said winding in resonant circuit relation, and means for producing a local control flux in a portion of said core which is orthogonal at least in part to the principal flux for varying the change in principal flux Without affecting the symmetry thereof.

2. The combination with a transformer having a core of magnetic material with an input drive and output winding on separate portions thereof inductively coupled by a principal magnetic flux traversing the core and having capacitor means coupled to the output winding in resonant circuit relation to produce a saturating magnetic flux in the secondary core portion, of a control winding passing through an opening in a flux carrying secondary portion of said core, and means for energizing said winding to produce a control flux orthogonal at least in part to the principal flux for reducing the change in principal flux for the same change in input drive.

3. In a transformer, a magnetic core, an alternating current input drive winding located on one portion of the core, means including an output winding located on an other portion of the core and having a capacitor coupled therewith in substantially resonant circuit relation, a magnetic shunt interposed between said windings, and a control Winding passing through a hole in a portion of the core for saturating a portion of the cross-sectional area of said portion immediately adjacent said hole.

4. In a transformer, a closed core of a magnetic material having primary drive and secondary windings on different portions thereof, a capacitor connected in circuit with a portion of the secondary winding for increasing the flux to effect saturation in the secondary portion, magnetic shunt means separating the primary and secondary portions and comprising a portion of the magnetic circuit for the secondary winding, and a figure 8 winding threaded through an opening in a portion of the secondary magnetic circuit for saturating a variable portion of the cross-section of said portion and reducing the change in flux for the same change in drive.

5. In a ferroresonant transformer, a magnetic core member, primary and secondary windings on separate portions of said core inductively related by a principal flux in said core member, a capacitor connected to a portion of said secondary winding to provide a resonant circuit condition and saturate said secondary core portion and means for producing in a portion of said secondary portion of the core member a control flux that is orthogonal to the principal flux.

6. In an alternating current ferroresonant regulating transformer, a core member having primary drive and secondary windings inductively coupled on portions of the core, a capacitor coupled with the secondary winding in resonant circuit relation for producing saturation in the secondary portion of the core, shunt means for diverting flux from one of said windings, and a control winding passing through an opening in said shunt member for producing a local control flux which is orthogonal in part to the diverted flux and changing the swing in the BH curve in the flux direction without changing the swing in the drive direction.

7. In a ferroresonant transformer, a magnetic core having primary and secondary portions with primary and secondary windings thereon, a capacitor connected across at least a portion of the secondary winding, a magnetic shunt interposed between said sections having an opening thereon, and a control winding passing through said opening for producing a local control flux in said shunt to alter the saturation characteristics thereof symmetrically.

8. A ferroresonant transformer comprising a magnetic core having separated primary and secondary windings alternating current on different portions, a magnetic shunt between said portions, a capacitor connected across at least a portion of the secondary winding to produce a substantially resonant circuit condition, and a figure 8 control winding passing through a hole in the secondary or shunt portion of the core for introducing a local control flux to vary the output voltage of the secondary winding.

9. The combination with a ferroresonant regulating transformer having a magnetic core with inductively coupled primary and secondary windings thereon, and means including a capacitor coupled in resonant circuit relation with the secondary winding for supplying alternating current to a load circuit, of a control winding passing through an opening in a portion of the core, and circuit means responsive to an electrical condition of the load circuit for effecting energization of the control winding to produce a magnetic flux in the immediate vicinity of the opening for regulating the output of the secondary winding without substantially distorting the output wave form.

10. In combination with a ferroresonant transformer having core portions with inductively coupled primary and secondary windings and an opening in one of said core portions, magnetic shunt means between said primary and secondary portions, means including a capacitor connected across a portion of the secondary Winding to provide a resonant circuit condition, a control winding passing through said opening for producing a local control flux, means including a source of reference voltage for producing a signal in accordance with a variation in voltage of the secondary winding, and means for effecting energization of the control Winding in response to said signal for regulating the voltage of the secondary Winding With- 8 alternating current power to a load circuit, capacitor means coupled to the secondary winding to produce a resonant circuit condition and saturate the secondary core References Cited in the file of this patent UNITED STATES PATENTS 2,143,745 Sole Jan. 10, 1939 2,800,625 Geroulo et a1. July 23, 1957 2,831,157 Grayson et al Apr. 15, 1958 2,844,804 Roe July 22, 1958 2,896,180 Brown July 21, 1959 2,904,743 McClain Sept. 15, 1959 3,012,187 Johnson Dec. 5, 1961 20 3,013,202 Kusko Dec. 12, 1961 

4. IN A TRANSFORMER, A CLOSED CORE OF A MAGNETIC MATERIAL HAVING PRIMARY DRIVE AND SECONDARY WINDINGS ON DIFFERENT PORTIONS THEREOF, A CAPACITOR CONNECTED IN CIRCUIT WITH A PORTION OF THE SECONDARY WINDING FOR INCREASING THE FLUX TO EFFECT SATURATION IN THE SECONDARY PORTION, MAGNECTIC SHUNT MEANS SEPARATING THE PRIMARY AND SECONDARY PORTIONS AND COMPRISING A PORTION OF THE MAGNETIC CIRCUIT FOR THE SECONDARY WINDING, AND A FIGURE 8 WINDING THREADED THROUGH AN OPENING IN PORTION OF THE SEOCONDARY MAGNETIC CIRCUIT FOR SATURATING A VARIABLE PORTION OF THE CROSS-SECTION OF SAID PORTION AND REDUCING THE CHANGE IN FLUX FOR THE SAME CHANGE IN DRIVE. 